leetcode First Bad Version

leetcode First Bad Version

You are a product manager and currently leading a team to develop a new product. Unfortunately, the latest version of your product fails the quality check. Since each version is developed based on the previous version, all the versions after a bad version are also bad.

Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one, which causes all the following ones to be bad.

You are given an API bool isBadVersion(version) which will return whether version is bad. Implement a function to find the first bad version. You should minimize the number of calls to the API.

题目地址： leetcode First Bad Version

题意：给定版本号从1~n，还有一个API bool isBadVersion(version) ，这个函数可以用来判断版本是否是错误的。 你的任务是最少次的调用这个API，来确定最先出错的位置

思路：

从版本出错的那个位置之后的版本也是错误的，所以很明显，二分即可。

1A水题

class Solution(object):
    def firstBadVersion(self, n):
        """
        :type n: int
        :rtype: int
        """
        L , R = 1 , n + 1
        while L < R :
            mid = L + ((R-L) >> 1)
            if isBadVersion(mid):
                R = mid
            else:
                L = mid + 1
        return L